Recessed florescent lighting accounts for a large percentage of the luminaires currently installed in commercial lighting around the world. Converting these florescent light fixtures into LED light fixtures can significantly reduce energy consumption. An LED module is essentially a surface mount electrical component that is soldered to a printed circuit board (PCB). As the lighting industry has begun to transition to using LED modules in light fixtures, there has been a tendency to produce LED strips having a linear array of LED modules mounted on them that mimic or emulate the familiar florescent light bulb.
FIG. 1 illustrates a typical florescent light fixture 2 having four florescent bulbs 3, known as T-8 bulbs, each having a one-inch diameter. Electrical power is supplied to the bulbs 3 via metal pins (not shown) that extending from opposite ends of each bulb 3 and are received by respective electrical contacts (not shown) located in tombstones 4 disposed in opposite ends of the fixture 2. Light from each of the bulbs 3 emanates radially outwardly from a center axis of the bulb 3. The florescent light fixture 2 is designed such that light that emanates radially outwardly from the bulbs 3 is reflected off of the inside surface 5 of the fixture 2. The goal of the fixture design is to create a uniform light distribution emanating from a plane that is parallel to the plane in which the inside surface 5 lies. The typical four-lamp T-8 florescent light fixture 2 consumes about 132 watts of power. Conversion to LED can result in substantial energy savings. Therefore, there is a demand for conversion solutions that convert florescent light fixtures into LED light fixtures.
FIG. 2 illustrates a perspective view of a typical LED strip 11 that is used to retrofit the typical four-lamp T-8 florescent light fixture 2 shown in FIG. 1 to convert it into an LED light fixture. The LED strip 11 is made to simulate the bulbs 3 of the florescent light fixture 2 and has metal pins 12 disposed on opposite ends thereof that are configured to engage with the electrical contacts of the tombstones 4.
Other types of LED conversion solutions have LED “bulbs” that also reuse the ballast of the florescent light fixture and strips that fasten to the florescent light fixture in various ways such that the fixture maintains the look of the original florescent bulb. The strip 11 has a linear array of LED modules 13.
One of the disadvantages of the known LED light fixtures of the type described above is that the LED modules of the strips or bulbs comprise sets of LED modules that are arranged in a linear array. For example, a strip may comprise a first set of four LED modules that are electrically connected to one another in series, a second set of four LED modules that are electrically connected to one another in series and linearly aligned with the LED modules of the first set, a third set of four LED modules that are electrically connected to one another in series and linearly aligned with the LED modules of the first and second sets, and a fourth set of four LED modules that are electrically connected to one another in series and linearly aligned with the LED modules of the first, second and third sets to forma linear array of sixteen LED modules. The four sets are connected in parallel. In such arrangements, if one of the LED modules fails, the other LED modules of that set also fail due to the series connection between the LED modules of the set.
Another disadvantage of the known LED light fixtures of the type described above is that they operate at high temperatures. The life expectancy of an LED module is primarily affected by the operating temperature of the LED module. An increase in operating temperature generally results in a reduction in life expectancy. Therefore, thermal management is an important consideration when designing an LED lighting solution. With the known LED strips and bulbs of the type described above, the thermal resistance to heat flow provided by the thermal management solution is so high that the LED modules operate at extremely high temperatures (i.e, several degrees above ambient temperature). Consequently, their life expectancies are relatively short.
Yet another disadvantage of the known LED light fixtures of the type described above is that they do not uniformly distribute light. If the LED strip 11 shown in FIG. 2 were used to retrofit the light fixture 2 shown in FIG. 1, typically two of the LED strips 11 would be used in the fixture 2. Unlike the florescent bulb 3 shown in FIG. 1 that emits light radially outwardly, some of which is reflected from the inside surface 5 of the fixture, the LED modules 13 of the LED strip 11 shown in FIG. 2 emit light in a conical pattern in a direction away from the top surfaces of the LED modules 13, and therefore the light would not be reflected from the inside surface 5 of the fixture 2. Because of the linear arrangement of the LED modules 13 in close proximity to one another, there is substantial overlap of the conical patterns, which results in areas of high-intensity light distribution where the overlap occurs and areas of substantially lower-intensity light distribution where there is no overlap. Also, the distribution of light in between the two LED strips 11 would have a lower intensity than the distribution of light directly beneath the strips 11. The result is a room illuminated with tremendous variations in light intensity levels. Consequently, such an LED light fixture has relatively low light distribution efficiency. In addition, the LED modules 13 are often overdriven with high electrical currents to increase illumination to compensate for the lack of uniformity in light distribution. Overdriving the LED modules 13 can further reduce their life expectancies.
A need exists for a cost-effective, efficient and reliable LED lighting solution that is a suitable retrofit solution for florescent light fixtures and that overcomes the aforementioned disadvantages. A need also exists for a cost-effective, reliable and efficient LED light fixture that is suitable is a new installation and that overcomes the aforementioned disadvantages.